1. Field of the Invention
The present invention relates to a device for discriminating the genuineness of bank note, and particularly to a magnetic detection device to be used in a bank note discriminating apparatus wherein the magnetic patterns formed on the bank notes by the magnetizable printing inks are detected by a magnetic detecting head to know the genuineness and kind of the bank notes.
2. Prior Art
A typical magnetic detection device used in a conventional bank note discriminating apparatus is shown in FIG. 1. In the illustrated prior art device, a bank note 2 is moved by a conveyer roller assembly 1 along a passage 4 formed by guide members 3. A magnetic detecting head 5 is arranged in the way of the passage 4. A press roller 6 opposes to the magnetic detecting head 5, and the bank note 2 is inserted in-between the head 5 and the roller 6 to be moved therethrough. The magnetic pattern born on the surface of the bank note 2 is detected by the magnetic detecting head 5 when the bank note is moved through the head 5. In the illustrated prior art device, the upper rollers 1 and 6 are biased downwards by the action of compression springs 7 to press the bank note 2 against the lower roller 1 and the magnetic detecting head 5. The device shown in FIG. 1 has a disadvantage that the bank note 2 tends to be folded or crimpled as it is inserted between the head 5 and the roller 6 since the press roller 6 is not rotated. This disadvantageous tendency is induced by the fact that no substantial gap is formed between the head 5 and the press roller 6.
In order to solve the aforementioned problem, a proposal has been made and disclosed by Japanese Utility Model Laid-Open Publication No. 54088/1978. The technique proposed by this preceding publication includes a press roller 6 which is preliminarily driven at a circumferential speed higher than that of the conveyer roller 1 to allow the bank note 2 to slip at the vicinity of the press roller 6 thereby to stretch the creases of the bank note 2.
However, in either of the devices shown in FIG. 1 and disclosed in Japanese Utility Model Laid-Open Publication No. 54088/1978, the press roller 6 is forced to abut against the magnetic head 5 by the biasing force of the spring 7 to clamp the bank note 2 so that the leading end of the bank note 2 comes into collision against the magnetic head 5 which in turn generates a noise signal upon collision with the leading end of each bank note. As a result, in such a conventional device, it is inevitable that the magnetic head 5 picks up a noise signal generated in proportion to the impulsive force which varies depending on the conveyed speed of the bank note 2. Moreover, since the press roller 5 rotates while being engaged with the face of the travelling bank note 2, vibrations due to elastic deformation or tottering of the press roller 6 induce further noise signals. For these reasons, accuracy in discriminating the bank note 2 is decreased as the conveying speed increases. Accordingly, the conventional device of this type has a disadvantage that the operational speed of the machine could not be increased.